U.S. Pat. No. 2,615,925 claims a process for producing a fluoroolefin by passing a mixture containing a chlorofluoro-compound over a metallic copper catalyst at 460.degree. to 700.degree. C. In an example 1,1,1,2-tetrachloro-2,2-difluoroethane and hydrogen were passed over a copper catalyst at 370.degree. C. to 390.degree. C. to obtain a 72% yield of 1,1-dichloro-2,2-difluoroethylene.
GB 698,386 discloses a process for making CClF.dbd.CF.sub.2 by passing a mixture of CCl.sub.2 FCClF.sub.2 (CFC-113) and hydrogen through an empty reactor at 450.degree. to 650.degree. C., or for higher efficiency through a reactor charged with a catalyst containing nickel, copper, cobalt, platinum, or palladium, either supported on carbon or unsupported, at 375.degree. to 525.degree. C. CClF=CF.sub.2 was produced in 52% yield while the major byproduct, CF.sub.2 .dbd.CHF was produced in 5% yield.
U.S. Pat. No. 2,942,036 discloses a process for the reaction of CF.sub.3 CCl.sub.2 CClF.sub.2 (CFC-215aa) with hydrogen over a palladium/carbon catalyst at 175.degree.-350.degree. C. to recover a product stream containing about 10% CF.sub.3 CCl.dbd.CF.sub.2, about 15-16% CF.sub.3 CH.dbd.CF.sub.2, about 60% CF.sub.3 CH.sub.2 CHF.sub.2, and about 6-7% unreacted CFC-215aa.
U.S. Pat. No. 3,043,889 discloses a process for making CClF.dbd.CF.sub.2 from CFC-113 and hydrogen by passing the mixture over a chromium oxide catalyst at 475.degree.-550.degree. C. Per pass conversions of CFC-113 of 15-30% were observed (col. 6, lines 17-30).
CA 655,397 claims a process for making CHF.dbd.CF.sub.2 in larger amounts than CH.sub.2 FCHF.sub.2 from CFC-113 by passing a mixture of hydrogen and CFC-113 over a Pd/C catalyst. The production of CClF.dbd.CF.sub.2 is inhibited by adjusting the mol ratio of H.sub.2 /CFC-113 to be in the range of 0.7-1.7. In a typical example, CFC-113 and hydrogen at 265.degree. C. are passed over a 1% Pd/C catalyst to obtain a 38% conversion to CHF.dbd.CF.sub.2 and a 25% conversion to CH.sub.2 FCHF.sub.2.
U.S. Pat. No. 3,505,417 discloses a process for the dehydrohalogenation of fluorohalocarbons using hydrogen over a catalytic composition consisting essentially of aluminum fluoride and at least one metallic element selected from groups I through VIII of the periodic table. The catalysts can also contain at least one metallic element which does not adversely affect their activity; some examples of which include: magnesium, barium, copper, sodium, potassium, chromium, nickel, molybdenum, vanadium, zinc, tin, silver, tungsten, iron, indium, titanium, germanium, platinum, palladium, rhodium, rhenium, osmium, and iridium. The patent claims a process for the dehydrohalogenation of fluorohalocarbons in the presence of hydrogen and a catalytic composition consisting of aluminum fluoride and from 0.05-30 weight percent of at least one of CuO, Cr.sub.2 O.sub.3, RhCl.sub.3, Co0, and Pt at 200.degree.-600.degree. C. When 1,2-dichloro-1,1,2,2-tetrafluoroethane (CFC-114) and hydrogen were passed over a copper oxide-cobalt oxide on fluorinated alumina catalyst, a 95% conversion of CFC-114 with a 78% yield of tetrafluoroethylene was obtained (Example 2).
U.S. Pat. No. 3,636,173 discloses a process and catalysts for the dehydrohalogenation of fluorohalocarbons using hydrogen and a catalytic composition containing aluminum fluoride and preferably a Group I-B, II-B, VI-B or Group VIII metal phosphate. Catalysts containing nickel or chromium phosphate are especially preferred. When CFC-113 and hydrogen were passed over a nickel phosphate catalyst at 385.degree. C, a 98% conversion of CFC-113 with a 54% yield of chlorotrifluoroethylene was obtained (col. 5, lines 40-48).
GB 1,578,933 discloses a process for the manufacture of CF.sub.3 CH.sub.2 F (HCF-134a) or CHF.sub.2 CHF.sub.2 (HFC-134) by the hydrogenolysis of an appropriate haloethane over a hydrogenation catalyst. Palladium supported on carbon or alumina are specifically claimed. In Ex. 3 a 94% conversion of CF.sub.3 CFCl.sub.2 (CFC-114a) with a 76% selectivity to HFC-134a and a 6.5% selectivity to CF.sub.3 CFHCl (HCFC-124)/CF.sub.2 HCF.sub.2 Cl (HCFC-124a) for the hydrogenolysis of CFC-114a over a Pd/C catalyst at 310.degree. C. is described.
C. Gervasutti et. al., J. Fluorine Chem., 19, 1 (1981) disclose the preparation of HFC-134a from the selective hydrogenolysis of isomeric mixtures of dichlorotetrafluoroethanes catalyzed by Pd/C to HFC-134a, CF.sub.3 CH.sub.3 (HFC-143a) and HCFC-124 with a selectivity of 77.8%, 12.6% and 9.7% respectively.
U.S. Pat. No. 4,319,060 discloses a process for producing CF.sub.2 ClCF.sub.2 Cl (CFC-114) substantially free of CFC-114a by the selective hydrogenolysis of a feed stream containing 0.1 to 25 weight percent of CFC-114a and 75 up to less than 100 weight percent of CFC-114 over a supported precious metal catalyst at 100.degree.-300.degree. C.
EP 164,954 discloses a method for the preparation of CF.sub.3 CHFCl (HCFC-124) from CF.sub.3 CFCl.sub.2 (CFC-114a) using an alkali metal amalgam in an active hydrogen containing (e. g., an alcohol) liquid medium.
The art shows that numerous catalysts, some of which are described above, for the hydrogenolysis and/or dehydrohalogenation of fluorohalocarbons are known. From the selectivities achieved in the art cited above, it is clear that there is a need for more selective catalysts. This need is particularly great because the products of these reactions are useful as environmentally desirable compounds for use as solvents, blowing agents and, particularly, refrigerants.
An object of this invention is to provide a process having improved selectivity and high conversion to the desired products.